1. Field of the Invention
The present invention relates to a flat-type semiconductor device and a packing thereof and, more particularly, to a packing of a flat-type semiconductor device which is suitable for transportation and a flat-type semiconductor device which is especially suitable for the packing.
2. Description of the Prior Art
A semiconductor device generally has a plurality of lead wires extend outward from the sides of a package in which a semiconductor element is sealed. The semiconductor device with straight lead wires is called a flat-type semiconductor device. A typical example of the flat-type semiconductor device is a quadral inline package (to be referred to as a QIP hereinafter). In a QIP, a package is made of a sealing resin layer and lead wires extend from the side surfaces of the sealing resin layer in four directions. A QIP type semiconductor device will be described as an example of the flat-type semiconductor devices.
FIG. 1 shows a QIP type semiconductor device which is ready to be delivered to a user. A semiconductor element (not shown) is sealed within a sealing resin layer 1. A plurality of lead wires 2 extend from the side surfaces of the sealing resin layer 1. The lead wires 2 are connected to the semiconductor element within the sealing resin layer 1.
The lead wires 2 are formed by punching a single metal plate. In the QIP type semiconductor device, the lead width and lead pitch are narrow. Accordingly, in consideration of manufacturing precision, the thickness of the lead wires is made thin. Therefore, the lead wires of the QIP type semiconductor device have low mechanical strength, resulting in their tendency toward deformation such as bending and distortion. For this reason, careful handling is required for the QIP type semiconductor device. Especially, when it is transported, the following packing method is adopted to prevent the deformation of the lead wires.
That is, as shown in FIG. 2, a packing material 3 made of, for example, polyurethane foam, in which a plurality of equidistantly spaced apart recesses 4 are formed, is used. The sealing resin layer 1 of the QIP type semiconductor device is stored in each recess 4. The size of the recess 4 is slightly larger than that of the sealing resin layer 1. So, the lead wires extend over the surface of the packing material 3, as shown in the figure. A plurality of QIP semiconductor devices are arranged in a plane in this manner. The recesses 4 are spaced apart from each other so as not to allow mutual contact between the lead wires 2. After the QIP semiconductor devices are arranged on the packing material 3 in a plane, they are stacked as shown in FIG. 3, and are packed in a carton box or the like for delivery.
If a packing as described above is used, deformation of the lead wires 2 of the QIP semiconductor devices during transportation can be prevented. Nevertheless, this packing has drawbacks to be described below. Firstly, since the QIP type semiconductor devices are arranged at intervals in a plane, packing density is low, so that transportation efficiency is degraded and transportation cost is increased. Secondly, it is difficult to automatically arrange the QIP type semiconductor devices on the packing material 3 in a plane. Similarly, it is also difficult to automatically take out the semiconductor devices one by one from the packing. This is partially attributable to the fact that the lead wires 2 are easy to deform. Thirdly, since a special packing material 3 is required, the packing cost is increased. Fourthly, the QIP type semiconductors are substantially symmetrical in four directions. Therefore, if the packing step is automatically performed, the QIP type semiconductor devices may be arranged in different directions.